1. Field of the Invention
The invention relates to a drive transmission switching mechanism in a recording apparatus, such as an ink jet printer, a facsimile and the like, and particularly to a drive transmission switching mechanism for switching to a state for transmitting a drive force of a driving source to negative pressure generating means and to a state for not transmitting it.
2. Description of Related Art
In the past, in recording apparatuses, such as an ink jet printer, a defective discharge occurs because bubbles occur in a printing head during use or ink droplets adhere to the surface of a nozzle. For the purpose of overcoming these problems and restoring a state to a good discharge state, the apparatus is provided with a maintenance device called a purge device. The purge device is designed so that a suction cap is placed over the printing head, and a negative pressure is generated by a pump to suck defective ink from within the printing head. It is known that a driving source, as means for generating the negative pressure, is used in common with a driving source for carrying a recording medium, such as printing paper, to reduce the number of parts and to reduce the cost.
The recording apparatus which uses in common the driving sources for the negative pressure generating means and the recording medium carrying means is provided with a drive transmission switching mechanism for switching the transmission of the drive force to the state where, when the negative pressure generating means is actuated, the drive force of the driving source can be a negative pressure transmitted to the generating means. In the drive transmission switching mechanism, a drive force transmission gear to which the drive force of the driving source is transmitted is selectively meshed with a drive gear of negative pressure generating means (hereinafter referred to as a negative pressure gear) or a drive gear of recording medium carrying means (hereinafter referred to as a carrying gear) whereby the drive force is transmitted to one or both of the gears. The transmission of the drive force to the negative pressure generating means by the drive force transmission gear is accomplished by moving the drive force transmission gear to a position meshed with the negative pressure gear when a carriage, having a printing head mounted thereon, moves to a position at which the printing head is capped by a protective cap provided on the recording apparatus (hereinafter referred to as a capping position).
However, in the above-described conventional drive transmission switching mechanism, in the case where the carriage moves from the capping position to another position, the drive force transmission gear is disengaged from the negative pressure gear even during the operation of the negative pressure generating means. Accordingly, in the case where the carriage is at the capping position, the power supply is turned off during the restoring operation with respect to the nozzle portion, and the user manually moves the carriage to a position other than the capping position during the turning-off of the power supply, the drive force transmission gear is disengaged from the negative pressure gear despite the fact that the restoring operation is not yet finished. Thus, it is difficult to return to the original operating state causing problems with recording by the recording apparatus. Further, in the case where the drive transmission switching mechanism as described above is provided on the color printer having a plurality of printing heads for jetting a plurality of colors of ink drops, when the restoring operation is sequentially carried out with respect to the nozzle portions of the printing heads by a single purge device, the carriage needs to sequentially move the nozzle portions of each of the printing heads to the position opposed to the purge device. Therefore, when the drive force transmission gear is disengaged from the negative pressure gear, it is not possible to smoothly carry out the restoring operation with respect to all the nozzle portions.